This invention relates to electromagnetic guns or projectile launchers. Conventional firearms are limited in muzzle velocity by the velocity of expansion of the propellant gases. Many prior art techniques have been used to achieve muzzle velocities approaching the limit dictated by the aforementioned velocity of expansion. These techniques have included the use of oversized barrels with a small projectile carried by a sabot down a long barrel. The use of lighter propellant gases with inherently higher expansion velocities has also been used, however powder charges capable of producing such gases are expensive and difficult to use.
Complex multiple state firearms have been developed to increase muzzle velocity. An example is shown in U.S. Pat. No. 4,057,002, issued on Nov. 8, 1977. This two stage gun includes a barrel which is mounted on a piston which is accelerated forward within a cylinder by means of a first propellant charge. When the barrel reaches a high velocity, a conventional cartridge chambered therein is fired automatically by the expanding gases of the first propellant. This results in a high muzzle velocity since the barrel velocity and the projectile velocity within the moving barrel are additive.
High muzzle velocities result in longer range and also higher target impact velocity which greatly enhances a projectile's terminal effectiveness.
Electromagnetic projectile launchers are not subject to the muzzle velocity limitation of conventional firearms and can achieve muzzle velocities of thousands of meters per second. Such devices are also known as electric guns, parallel rail launchers or rail guns. In such projectile launchers the projectile is usually mounted on a conductive armature which is adapted to slide between a pair of parallel projectile or launching rails. A very high direct current is injected into the rails so that the current passes through the projectile armature. The resulting electromagnetic field drives the projectile armature down the rails at high speed. The high direct current is commutated into the projectile rails by means of a rail switch which is connected in series with a charging inductor through which a high direct current is flowing. The rail switch shorts or bridges the projectile rails before firing so that when the rail switch is opened the high direct current is applied to the projectile rails and to the projectile armature assembly. The rail switch may comprise a second rail gun comprising a pair of parallel switching rails with a moveable switching armature slidably mounted therebetween.
In the prior art, projectile armatures have been positioned at the breech end of the projectile rails while the inductive energy storage device was charging and while the rail switch was operating to commutate the high accelerating current into the projectile rails. This arrangement permitted parasitic currents to flow through the projectile armature prior to and during the opening of the rail switch. This resulted in undesired heating of the projectile armature and/or movement thereof. Also. when commutation took place, the resulting high projectile armature currents coupled with the low initial speed of this armature sometimes resulted in welding of the armature to the projectile rails, or damage to the rails caused by this heating.
One prior art solution to this problem is shown in U.S. Pat. No. 4,369,691, issued on Jan. 25, 1983. In this patent, the breech area of the projectile rails includes a resistive insert which is contacted by the stationary projectile armature before firing and during charging of the inductive energy storage device. Thus premature excessive heating and projectile armature welding problems are obviated since the parasitic currents are reduced by the resistive inserts, however this apparatus results in reduce initial acceleration while the projectile armature remains within the resistive inserts, and this reduces the efficiency cf energy transfer to the moving projectile armature.
The present invention overcomes the aforementioned disadvantages in a novel manner so that energy transfer to the projectile armature is maximized and the kinetic energy of the switching armature is utilized to accelerate the projectile armature.